The invention relates to an apparatus and a method of monitoring the air pressure in a pneumatic tire carried by the rim of a vehicle wheel, comprising a sensing element which is arranged at the rim ring and which can be deformed and acted upon by the tire pressure, with a permanent magnet as a measurement value generator, wherein arranged in the region of rotary movement thereof is a measurement value sensor which is fixed to the vehicle in a stationary position and which is connected to an evaluation circuit.
In an apparatus of that kind, as set forth in German laid-open application (DE-OS) No. 30 37 722, the sensing element is in the form of a pressure generator with a suction circuit which can be influenced by the air pressure, being fixed to each tire of a motor vehicle. The pressure generator co-operates with a fixed pick-up which is connected to a free-oscillating oscillator device and to an evaluation circuit for computation and display of the tire pressure.
Such an arrangement suffers from involving very high production costs, for which reason the inventor set himself the aim of providing a simple apparatus of the kind set forth in the opening part of this specification, which is reliable in operation and which is provided with an uncomplicated evaluation device. An essential aspect of the invention is also the provision of an inexpensive apparatus of that kind, and the elimination of uncertainties in electronic monitoring.